In a paper about to be published in The Proceedings of the Royal Society, a team of researchers identifies something they call the "paradox of unanimity." If you've ever smelled a rat when everyone else is celebrating an idea then this paradox is for you. While unanimous agreement (or something close to it) might suggest that a particular claim is right, the researchers, led by Lachlan J. Gunn, an engineer at the University of Adelaide in Australia, found the opposite to be true. Rather than confirming truth, unanimity indicates that something went wrong, that a "systemic failure" undermined popular judgment, that the confidence of the crowd has been skewed by bias.

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As it's currently framed, the paradox applies primarily to criminal justice concerns—police line-ups and the like. But it also has implications for food and agriculture. Few fields of popular interest have cultivated a wider array of glib axioms of empowerment than food: genetically modified organisms are bad, local is better, you shouldn't eat food your grandmother wouldn't eat, and so on. In the context of Main Street foodie wisdom, these claims enjoy something close to unanimity. But, for all their support, none comes closer to the unanimity quotient than the gilded assertion that organic food is food grown without pesticides.

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Few fields of popular interest have cultivated a wider array of glib axioms of empowerment than food.

The message is widespread. After widely publicizing a list of produce—"The Dirty Dozen"—with comparatively high (but legal) levels of pesticide residue, the Environmental Working Group recommends "that people who eat a lot of these foods buy organic instead." To "avoid pesticides in your food," Tracey Ternes, writing on the website of a leading organic retailer, instructs, "buy local, organic food whenever possible." And here's EcoWatch's advice: "The best way for consumers to avoid pesticides in food is to purchase organic produce if possible." Stop anyone in the grocery store choosing organic produce. Ask them why. Chances are good the answer will be to "avoid pesticides."

Enter into this conventional belief the paradox of unanimity. This time the buzz kill comes from the Department of Agriculture's (USDA) recently released annual summary for pesticide data program. According to this survey, 21 percent of the 409 organic samples of produce tested by the USDA showed evidence of synthetic pesticide residues. What's notable about this already high percentage is that the residue detection test doesn't even measure commonly used organic pesticides like copper and sulfur compounds, mineral oil, and bacillus thuringiensis (Bt). According to Steve Savage, who wrote about the report for Forbes, if organic pesticide residues were measured, "the detection percentage for organic would be much higher." So, score one for the unanimity paradox, one that, this time, may save you money at Whole Foods.

What's exciting about this paradox is not only that it turns sacred truths into flimsy myths, but that in doing so it offers an opportunity to explore a) the bias that led to our error, and b) an explanation for the newly discovered reality. For organic produce, it seems safe to say that the bias derived from our irrational belief in food purity. The idea that our food can be "all natural" is rooted in a deeply romanticized idea about farming, one that categorically fails to consider the long-term genetic changes imposed on food to make it food, much less the impact that pests can have on agricultural yield. We would do well to re-consider out relationship to this jejune notion.

But what's more interesting in this case is the possible explanation. Why was there synthetic residue on organic crops? The most logical culprits are drift from nearby farms growing crops conventionally and cross contamination from the bins used for harvesting both organic and conventional crops (many farms grow both). "Many of the detections are at such low levels they fit th[e]se scenarios," according to Savage. In other words, yes, makes sense.

One likely response to the drift dilemma is to argue that organic produce deserves better protection. That perhaps there should be laws requiring conventional agriculture to keep its distance from the organic good guys. But the problem with this objection is not only that, as indicated, many farmers grow both organically and conventionally, but that (as a conventional apple grower once told me) organic farmers sometimes want to be around the conventional growers because pesticide drift helps reduce pests on their farms as well.

But there's a final, more controversial point to consider. In his Forbes piece, Savage noted something that might raise eyebrows: "When I looked at the conventional detections for the same 78 chemical/crop combinations, the organic detections were only significantly lower in 26 cases, and the organic detections were equal to or higher than those in conventional for 30 cases." Implication? Well, Savage never spells it out, and in an email he explained that he has no way of knowing for sure, but the possibility does cross my mind: illicit spraying by the organic growers.

My guess is that, within the foodie world, there will be agreement against this charge. And, surely, it'll be unanimous.